 /*******************************************************************************
  * Copyright (c) 2004, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.commands;

 import org.eclipse.core.commands.common.AbstractBitSetEvent;

 /**
  * An instance of this class describes changes to an instance of
  * <code>IHandler</code>.
  * <p>
  * This class is not intended to be extended by clients.
  * </p>
  *
  * @since 3.1
  * @see IHandlerListener#handlerChanged(HandlerEvent)
  */
 public final class HandlerEvent extends AbstractBitSetEvent {

     /**
      * The bit used to represent whether the handler has changed its enabled
      * state.
      */
     private static final int CHANGED_ENABLED = 1;

     /**
      * The bit used to represent whether the handler has changed its handled
      * state.
      */
     private static final int CHANGED_HANDLED = 1 << 1;

     /**
      * The handler that changed; this value is never <code>null</code>.
      */
     private final IHandler handler;

     /**
      * Creates a new instance of this class.
      *
      * @param handler
      * the instance of the interface that changed; must not be
      * <code>null</code>.
      * @param enabledChanged
      * Whether the enabled state of the handler has changed.
      * @param handledChanged
      * Whether the handled state of the handler has changed.
      */
     public HandlerEvent(final IHandler handler, final boolean enabledChanged,
             final boolean handledChanged) {
         if (handler == null) {
             throw new NullPointerException ();
         }
         this.handler = handler;

         if (enabledChanged) {
             changedValues |= CHANGED_ENABLED;
         }
         if (handledChanged) {
             changedValues |= CHANGED_HANDLED;
         }
     }

     /**
      * Returns the instance of the interface that changed.
      *
      * @return the instance of the interface that changed. Guaranteed not to be
      * <code>null</code>.
      */
     public IHandler getHandler() {
         return handler;
     }

     /**
      * Returns whether or not the enabled property changed.
      *
      * @return <code>true</code>, iff the enabled property changed.
      */
     public boolean isEnabledChanged() {
         return ((changedValues & CHANGED_ENABLED) != 0);
     }

     /**
      * Returns whether or not the handled property changed.
      *
      * @return <code>true</code>, iff the handled property changed.
      */
     public boolean isHandledChanged() {
         return ((changedValues & CHANGED_HANDLED) != 0);
     }
 }

